This invention is concerned with a disc brake comprising a disc mounted for rotation with a hub, friction material pads mounted on opposite sides of said disc, and operating means operable to cause the pads to engage opposite sides of the disc to cause braking of the disc and hence of the hub.
In a conventional disc brake of the spot type, the pads each comprise a block of friction material mounted on a backing plate. The backing plates are mounted, either fixedly or for movement towards the disc. Whether the mounting is fixed or for movement depends on the position of the operating means relative to the assembly and on the type of brake. Where the brake is of the sliding-caliper type and the operating means, eg a hydraulically-operated piston and cylinder assembly, is on one side of the disc, the block and backing plate on the operating means side of the disc is moveably mounted while the other block and backing plate can be fixedly-mounted on the caliper. When the friction material becomes worn, the block and backing plate are replaced, with the backing plate generally being thrown away.
Conventional pad assemblies for disc brakes are manufactured by positioning a backing plate across an opening of a die cavity containing curable particulate material, compressing the particulate material against the backing plate to form a block adhered to the backing plate, and curing the material. However, this is a complex operation and it is difficult to ensure that the block adheres sufficiently to the backing plate to withstand the very high shearing forces encountered during braking. Indeed, special measures are often taken to improve adhesion, eg projections or recesses of the backing plate may be provided to key the plate and the block together. (See for example GB 2259553 A and DE 2365508 A.)